硅粉增强混凝土抗冲磨性能的微观机理

本文采用Fourier红外光谱(FTIR)和29Si固体核磁共振谱(29Si NMR)结合去卷积技术研究了硅粉增强混凝土抗冲磨性能的微观机理。结果表明硅粉具有较高的水化活性，硅粉掺量为10%的水泥体系水化3d时，大约有41%的硅粉参与反应，水化120d时大约有96%的硅粉参与反应。此外，硅粉的火山灰反应改变了C-S-H结构中Qn的分布和C-S-H的聚合度，在这个过程中，硅粉结构中的Si-O-Si共价键在碱性环境中断裂后形成的水化硅酸根单体与C-S-H二聚体以及Ca2+、OH-结合，形成高聚C-S-H。在分子尺度(几个纳米)，硅粉优化了C-S-H结构，使得C-S-H结构有序性增强，在微米尺度，硅粉的火山灰反应使得C-S-H堆积结构更加密实，胶凝性更强，从而改善了混凝土中浆体的性质。这样就从C-S-H层面解释了硅粉改善混凝土强度以及抗冲磨性能的机理。

Study of the Microstructural Mechanism to Improve the Abrasion Resistance of Concrete by Adding Silica Fume

The mechanism to improve the abrasion resistance of concrete by adding silica fume was studied by Fourier transform infrared spectroscopy, high resolution 29Si MAS NMR with deconvolution technique, respectively. The results of FTIR and 29Si MAS NMR indicated that SF possesses an high pozzolanic reactivity. About 41% of SF at 3d and about 96% at 120d has reacted in a paste containing 10% SF (by weight of cement replacement). After the covalent bonds of Si-O-Si in SF were broken, monomers formed, which can connect C-S-H dimers to form highly polymerized C-S-H, and increased the average chain length (ACL) of aluminosilicate. At the molecule scale, the incorporation of SF made the C-S-H more long-range order and better organized, at the colloidal-scale, the C-S-H particles bond denser and the quality of pastes was improved, both of which may explain form the point of C-S-H why the compressive strength of hardened cement paste and abrasion resistance of concrete was improved.